GB948367A - Improvements relating to scanning circuit arrangements - Google Patents

Abstract

948,367. Automatic exchange systems. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. June 27, 1962 [July 31, 1961], No. 27720/61. Heading H4K. In an arrangement for scanning line circuits, 10,000 coincidence gates G one for each line circuit are divided into 10 groups GR1 . . . GR10 in each of which the gates are disposed in co-ordinate fashion in 10 columns and 100 rows, and a cyclic counter PC supplies pulses in succession to the columns of the first group, then to those of the second group and so on. The outputs from each row of gates are multipled and taken to gates (1) OG1 . . . (1) OG100 and so on, and the corresponding output gates from the various groups, e.g. (1) OG1 . . . (10) OG1 are pulsed in succession by a second cyclic counter SC which delivers a pulse for each cycle of the counter PC. The functions of the two counters may be interchanged, in which case the order of scanning is altered. The arrangement may be used for detecting a particular condition, such as a line circuit locked out as the result of a permanent loop, when a characteristic bias is applied to the input Vm of the corresponding gate. Assuming that such a condition exists, the coincidence of pulses from PC, SC on the relevant detection gate, e.g. G1, and output gate, e.g. (1) OG1, results in a pulse on lead ogl which sets a bistable element BE and thus stops the generator 1G driving the counters PC, SC. A signal on lead il indicates to an external circuit that the identity of the marked circuit is available over leads mpc, msc, and when this information has been transferred, a signal on lead sl resets BE and restarts scanning. If the external circuit can respond quickly enough to the identity signals, the stoppage of scanning becomes unnecessary and the circuit BE is not required. The scanning arrangement is described in greater detail with reference to Figs. 2-4 (not shown).